1. Field of the Invention
The present invention relates to a fabrication method for an electrode active material and a lithium battery comprising an electrode active material fabricated therefrom, and more particularly, to a fabrication method for an electrode active material capable of implementing an excellent life span and high performance by utilizing a precursor, the precursor prepared by undergoing positive ion substitution and surface-reforming processes through one process without using a chelating agent, and a lithium battery comprising an electrode active material fabricated therefrom.
2. Description of the Background Art
Metallic compounds and phosphorous oxides being currently used as a cathode active material for lithium secondary batteries include LiCoO2, LiMn2O4, LiMnO2, LiNiO2, LiNiCoO2, V6O13, V2O5, LiFePO4, Li3Fe2(PO4)3, etc. Transition metallic oxides used as an anode active material include Li4Ti5O12, etc. A cathode active material for lithium primary batteries includes MnO2, etc.
These materials are generally fabricated by a solid phase method. During the fabrication process, the electrode active materials have to be mixed and crushed in a physical manner. Accordingly, a mixed state of the electrode active materials becomes non-uniform. This causes repetitive sintering and crushing processes, thereby increasing fabrication costs and fabrication duration. Furthermore, after the repetitive sintering and crushing processes, there may occur problems in uniformity of particle sizes and in homogeneity of chemical composition.
Charging and discharging processes for lithium batteries are performed by a diffusion process of lithium ions. Accordingly, uniformity of particle sizes and homogeneity of chemical composition greatly influence on characteristics of electrodes (cathode, anode) for lithium batteries. Accordingly, it is very important to control uniformity of particle sizes and homogeneity of chemical composition. In order to enhance characteristics of an electrode active material, a small amount of hetero-element may be doped or a surface-reforming process may be performed. However, in this case, the homogeneity of chemical composition may severely deteriorate.
In order to solve the problems of the solid phase method, a liquid phase method has developed. A representative of the liquid phase method includes a sol-gel process (A. Manthiram et al., chemistry of Materials, 10, pp 2895-2909 (1998)). When transition metallic oxide powder is fabricated by using the sol-gel process composed of hydrolysis and condensation, lithium ions and transition metallic ions are mixed in nano sizes, thereby having a particle size much smaller that that of powder fabricated by a solid phase method. Accordingly, by the sol-gel process, an electrode active material having a large surface area, a uniform particle size, and a uniform composition can be obtained. Furthermore, the sol-gel process can reduce fabrication time since repetitive sintering and crushing processes are not required, and can reduce fabrication costs since an electrode active material can be synthesized at a lower temperature than in a solid phase method. Accordingly, the sol-gel process is effective to uniformly synthesize electrode active material powder for a lithium battery in nano size, or to dope a hetero-element.
However, the sol-gel process is not effective to a surface-reforming process, and requires an additional chelating agent. Furthermore, the sol-gel process causes a difficulty in a massive production due to its complicated processes.